This invention relates to an apparatus for growing a semiconductor crystal and a method of growing the same, and in particular, to a crystal growing technique for rotating semiconductor melt (or solution) by applying a magnetic field and current which cross each other in the semiconductor melt.
A semiconductor crystal wafer used as a substrate of a super highly integrated electronic device is generally grown by the use of the Czochralski method hereinafter, abbreviated as the CZ method).
In the CZ method, the semiconductor crystal wafer is grown by pulling a semiconductor single crystal from a rotating semiconductor melt while rotating the semiconductor single crystal in an opposite direction to that of the semiconductor melt.
With such an arrangement, the semiconductor melt is retained in a crucible which is heated by a cylindrical heater which is arranged around the crucible. Using this arrangement, the crucible is rotated so as to ensure uniform temperature distribution in the semiconductor melt.
To this end it is necessary that a rotating center of the crucible and a symmetrical axis of heater arrangement correspond to the pull axis of the semiconductor crystal in order to ensure even temperature distribution in the semiconductor melt symmetrical with the axis.
In general, the axis for holding the crucible is mechanically rotated in a conventional manner.
However, a large apparatus is required to rotate a crucible used for growing large size crystals. Consequently, the growth of large semiconductor crystals is difficult.
To solve such difficulty, an apparatus for growing a semiconductor crystal and a method of growing the same has been proposed in unpublished, Japanese Patent Application No. Hei. 9-343261, which.
This semiconductor crystal growing apparatus includes a device to applying a magnetic field for semiconductor melt during growth of a semiconductor crystal and another device for applying current perpendicular to the magnetic field of the semiconductor melt.
Further, an electrode which is immersed in the semiconductor melt and another electrode which supplies current to pull a semiconductor crystal are used in the above semiconductor crystal growing apparatus.
In this semiconductor crystal growing apparatus, even when a semiconductor crystal having a large diameter of 30 cm or more is grown, the size of the apparatus is minimized, and it is possible to accurately control rotation.
However, when electrode material is dissolved into the semiconductor melt and the electrode material contains material other than the semiconductor melt and the growing semiconductor crystal, the purity of the semiconductor melt and the growing crystal is degraded. This produces an adverse affect for the other impunity concentration distribution.
Moreover, when the electrode is immersed into the semiconductor melt, the rotation of the semiconductor melt is partially interrupted by the electrode. As a result, symmetry of the rotation is also degraded.